The present invention relates to a structure and a method for branching a conductive wire from a shielded wire which including a core conductive wire and an insulating sheath.
A related-art example of this kind has been disclosed in Japanese Patent Publication No. 4-269470A shown in FIGS. 17 and 18.
In a branching structure shown in FIG. 17, an insulating outer sheath 101 provided in the vicinity of the end of a shielded wire 100 is partially peeled and a braided wire 102 to be a shielding cover is exposed. An insulating outer sheath 104 provided on the end of a grounding wire 103 is peeled to expose a conductive wire 105. The braided wire 102 of the shielded wire 100 and the conductive wire 105 of the grounding wire 103 are pressed and fixed through a coupling member 106.
In a branching structure shown in FIG. 18, an insulating outer sheath 111 provided on the end of a shielded wire 110 is peeled to expose a drain wire 112, and the drain wire 112 thus exposed is used as a grounding wire.
However, both of the branching structures have a problem in that the number of steps is great and a large number of manual works are to be carried out. For this reason, automation cannot be achieved;
A related branching structure to solve such a problem has been disclosed in Japanese Patent Publication No. 11-135167A shown in FIGS. 19 and 20.
In the branching structure shown in FIGS. 19 and 20, a braided wire 120d of a shielded wire 120 is electrically connected to a conductive wire 123a of a grounding wire 123 by an ultrasonic horn 125 through a pair of resin members 121 and 122.
In other words, the shielded wire 120 is constituted by one shielding core 120c having a core 120a covered with an insulating inner sheath 120b, a conductive braided wire 120d for covering the outer periphery of the shielding core 120c, and an insulating outer sheath 120e for further covering the outer periphery of the braided wire 120d. A pair of resin members 121 and 122 have concave portions 121b and 122b for forming a hole corresponding to the outer sectional shape of the shielded wire 120 with mutual bonding faces 121a and 122a buffed against each other, respectively. The grounding wire 123 is constituted by the conductive wire 123a and an insulating outer sheath 123b for covering an outer periphery thereof. The ultrasonic horn 125 is constituted by a lower support base (not shown) provided in a lower part and an ultrasonic horn body 125a provided in an upper part.
Next, a blanching procedure will be described. The lower resin member 122 is provided on the lower support base (not shown) of the ultrasonic horn 125, the shielded wire 120 is mounted from thereabove, one end of the grounding wire 123 is mounted thereon, and furthermore, the upper resin member 121 is put from thereabove. Thus, the shielded wire 120 is provided In the concave portions 121b and 122b of the resin members 121 and 122, and the grounding wire 123 is provided between the shielded wire 120 and the upper resin member 121.
In this state, a vibration is applied by the ultrasonic horn 125 while applying compression force between the resin members 121 and 122. Consequently, the insulating outer sheath 120e of the shielded wire 120 and the Insulating outer sheath 123b of the grounding wire 123 are fused and scattered by the internal heat generation of a vibration energy so that the conductive wire 123a of the grounding wire 123 and the braided wire 120d of the shielded wire 120 come in electrical contact with each other. Moreover, each of the contact portions of the bonding faces 121a and 122a of the resin members 121 and 122, the contact portion of the internal peripheral faces of the concave portions 121b and 122b of the resin members 121 and 122, the insulating outer sheath 120e of the shielded wire 120, the contact portion of the insulating resin 123b of the grounding wire 123, and the resin members 121 and 122 are fused by the heat generation of the vibration energy and the fused portions are solidified after the ultrasonic vibration is completely applied. Consequently, the resin members 121 and 122, the shielded wire 120 and the grounding wire 123 are fixed to each other.
According to the branch processing, it is not necessary to peel the insulating outer sheaths 120e and 123b of the shielded wire 120 and the grounding wire 123, and the lower resin member 122, the shielded wire 120, the grounding wire 123 and the upper resin member 121 are simply assembled in this order to give the ultrasonic vibration. Consequently, the number of steps is decreased, and a complicated manual work is not required and automation can also be achieved.
Accordingly, the grounding wire 123 of the shielded wire 120 is thus caused to branch so that a noise flowing through the core wire 120c can be caused to escape from the braided wire 120d toward the ground through the conductive wire 123a of the grounding wire 123.
In such a wire branch processing, however, the shielding cover of the shielded wire 120 is the braided wire 120d. Therefore, the contact of the braided wire 120d with the conductive wire 123a has a relationship in which the surfaces of sectional circular lines come in contact with each other and their contact area is decreased so that their connecting reliability is deteriorated as shown in FIG. 19.
Moreover, the contact area of the braided wire 120d and the conductive wire 123a is decreased so that the amount of escaped noise is reduced. Consequently, a drain wire (not shown) is provided in the shielded wire 120 to maintain the amount of escape of the noise. In this case, it is necessary to additionally provide the drain wire. Therefore, the number of members is increased with a complexity of the structure so that the cost of the shielded wire 120 is increased, and furthermore, a weight becomes greater.
In the branching structure, the single core type shielded wire 120 can be properly shielded. However, if the same structure is applied to a multicore type shielded wire having a different internal configuration, the following drawbacks would be occurred.
More specifically, a multicore shielded wire has such a structure that a plurality of shielded core wires are accommodated with a clearance in the internal space of an insulating outer sheath and a braided wire. For this reason, the degree of a close contact and the arrangement relationship between the braided wire and the shielded core wires are indefinite with an interposition between the resin members 121 and 122. In some cases in which the degree of a close contact is excessive, the insulating inner sheath of the shielded core wire is broken or cut upon receipt of the transmission of great vibration energy. Consequently, the grounding wire or the shielding cover comes in contact with the core to cause a short circuit, and furthermore, the strength of the multicore shielded wire is reduced.
In order to eliminate such a drawback, it can be proposed that the vibration energy to be applied by the ultrasonic vibration is reduced. However, in such a condition, a bonding strength based on the fusion and solidification between the resin members 121 and 122 is accordingly reduced.
It is therefore a first object of the present invention to provide a structure and a method for branching a shielded wire in which the connecting reliability of a branch wire branched from the shielded wire can be enhanced and the structure can be simplified to decrease the number of members.
It is a second object of the invention to provide a structure and a method for branching a multicore shielded wire in which a pair of resin members can be connected firmly, and furthermore, a short circuit can be prevented from being caused by the contact of a grounding wire or a shielding cover with a core wire so that the strength of the multicore shielded wire can be prevented from being reduced.
In order to achieve the above objects, according to the present invention, there Is provided A shielded wire, comprising;
at least one shielded core wire, in which a first conductive core wire is covered with a first insulating sheath;
a conductive foil, which covers the at least one shielded core wire;
a second Insulating sheath, which covers the conductive foil; and
a branch wire, in which a second conductive core wire is covered with a third insulating sheath;
wherein a part of the second insulating sheath and a part of the third insulating sheath are thermally fused so that the conductive foil and the second conductive core wire are electrically connected.
In this configuration, when the second conductive wire of the branch wire is connected in contact with the conductive foil, their contact area can be increased so that the connecting reliability of the branch wire to branch from the shielded wire can be enhanced.
In the case in which the branch wire is used as an earth wire, a noise passing through the core wire can be caused to efficiently escape through the branch wire so that an extra drain wire can be eliminated from the shielded wire. Consequently, the number of members constituting the shielded wire can be decreased and the structure can be simplified so that an inexpensive shielded wire can be provided, and furthermore, the weight of the shielded wire can be reduced.
Preferably, the shielded wire further comprises a reinforcing member provided on an inner face of the conductive foil.
In this configuration, since the conductive foil can be reinforced by the reinforcing foil member, even when the shielded wire is subjected to press contact operation, the deformation of the conductive foil can be suppressed. Therefore, the contact area of the conductive foil and the second conductive wire can be maintained more reliably.
Here, it is preferable that the reinforcing member is a polyester sheet.
In this configuration, the conductive foil can be reinforced strongly while maintaining the appropriate flexibility of the shielded wire.
Preferably, a space between the conductive foil and the at least one shielded core wire is filled with an insulating material having a heat-resistant property.
In this configuration, particularly in a case where a multicore shielded wire is adopted, a plurality of shielded core wires are seldom moved by the Insulating material filled in the conductive cover foil. Therefore, it can be prevented the displacement of the shielded core wires due to a press contact operation or an ultrasonic vibration in ultrasonic welding or the like. Moreover, the position of the conductive foil is also stabilized by the insulating material.
In addition, since the outer periphery of the shielded core wire is covered with the heat-resistant insulating material, the first insulating sheath of the shielded core wire is neither broken nor cut by heat generation caused by the ultrasonic vibration.
Alternatively, the shielded wire further comprises a drain wire provided inside of the conductive foil.
In this configuration, since the shielding can also be carried out by earthing the drain wire, there is an advantage that a variation in a countermeasure against the shielding can be increased correspondingly.
In order to attain the same advantages, according to the present invention, there is also provided a shielded wire, comprising:
at least one shielded core wire, in which a first conductive core wire is covered with a first insulating sheath;
a conductive cover member, which covers the at least one shielded core wire;
a second insulating sheath, which covers the conductive foil; and
a branch wire, in which a second conductive core wire is covered with a third insulating sheath,
wherein a part of the second insulating sheath and a part of the third insulating sheath are thermally fused so that the conductive foil and the second conductive core wire are electrically connected; and
wherein a space between the conductive foil and the at least one shielded core wire is filled with an insulating material having a heat-resistant property.
Preferably, the conductive cover member is a metal foil.
Here, it is preferable that the shielded wire further comprises a reinforcing member provided on an inner face of the conductive foil.
Here, it is preferable that the reinforcing member is a polyester sheet.
Preferably, the shielded wire further comprises a drain wire provided inside of the conductive foil.
In order to achieve the above objects, according to the present invention, there is also provided a method of branching a sheathed wire from a shielded wire, comprising the steps of:
providing at least one shielded core wire, in which a first conductive core wire is covered with a first insulating sheath;
covering the at least one shielded core wire with a conductive cover member;
covering the conductive cover member with a second insulating sheath to constitute the shielded wire;
providing the sheathed wire in which a second conductive core wire is covered with a third insulating sheath;
providing a pair of resin members, in which a bonding face including a groove is formed in each resin member and at least one protrusion is formed on at least one of the bonding faces;
sandwiching the shielded wire and the sheathed wire between the pair of resin members such that the grooves face with each other while accommodating the sheathed wire therein;
applying ultrasonic vibration such that ultrasonic waves are concentrated to the protrusions to thermally fuse at least the protrusion so that the bonding faces of the resin members are integrated with each other, while thermally fusing a part of the second insulating sheath and a part of the third insulating sheath so that the conductive cover member and the second conductive core wire are electrically connected.
In this configuration, when the ultrasonic vibration is started to be applied in this state, the vibration energy concentrates on the protrusion so that the resin members are sufficiently fused and firmly come in close contact with each other in the vicinity of the mutual bonding faces. By such concentration of the vibration energy in the protrusions, the vibration energy to be applied to the grounding wire or the shielded core wire can be reduced. Consequently, the first insulating sheath can be prevented from being broken or cut due to the fusion caused by the transmission of an excessive vibration energy. Accordingly, the resin members can be connected firmly, and furthermore, a short circuit can be prevented from being caused by the contact of the branch wire or the conductive cover member with the first conductive core wire, and therefore the strength of the multicore shielded wire can be maintained.
Preferably, the protrusion includes a pair of protrusions formed at both sides of at least one of the groove so as to extend therealong.
In this configuration, the vibration energy concentrates on the protrusion in any position in the axial direction of the shielded wire. Consequently, it is possible to uniformly reduce the vibration energy to be applied to the shielded core wire in the axial direction of the shielded wire.
Preferably, the protrusion includes two pairs of protrusions formed at both sides of the grooves so as to be abutted on each other in the sandwiching step.
In this configuration, a pair of resin members can have the same shape. Consequently, there is an advantage that the manufacturing cost of the resin member can be reduced and the resin members can be handled easily.
Preferably, the second conductive core wire is a plated wire having a melting temperature which is lower than a temperature of an internal heat generated by the ultrasonic vibration.
In this configuration, the plated wire is partially fused to come in contact with the conductive cover member by the vibration energy. Consequently, it is possible to enhance a reliability in the contact portion of the conductive cover member of the shielded wire and the second conductive core wire of the sheathed wire.
Preferably, the branching method further comprising the steps of providing an ultrasonic horn for applying the ultrasonic vibration, and contacting a contact face of the ultrasonic horn with a contact face of one resin member. Here, at least one of the contact face of the ultrasonic horn and the contact face of the resin member is formed with a recessed portion.
In this configuration, the vibration generated from the ultrasonic horn body is transmitted to the shielded wire through the resin member provided in contact therewith. The ultrasonic horn body and the resin member are provided in contact with each other in a small area by the recessed portion. Therefore, the vibration to be applied to the conductive cover member is reduced through the resin member so that the shield covering member is neither broken nor cut due to the ultrasonic vibration and heat generation. Accordingly, the electrical contact of the sheathed wire and the shielded wire can be obtained reliably so that an electric performance can be enhanced, and furthermore, the strength of the shielded wire can be maintained.
Here, it is preferable that the recessed portion is situated at a position opposing to a position at which the conductive cover member and the second conductive core wire are electrically connected.
In this configuration, the vibration to be transmitted at the shortest distance from the ultrasonic horn body to the electrical contact portion of the shielded wire and the sheathed wire though the resin member does not act. Consequently, it is possible to effectively reduce the vibration to be applied to the electrical contact portion.
In order to attain the same advantages, according to the present Invention, there is also provided a method of branching a sheathed wire from a shielded wire, comprising the steps of:
providing at least one shielded core wire, in which a first conductive core wire is covered with a first insulating sheath;
covering the at least one shielded core wire with a conductive cover member;
covering the conductive cover member with a second insulating sheath to constitute the shielded wire;
providing the sheathed wire in which a second conductive core wire is covered with a third insulating sheath;
providing a pair of resin members, in which a bonding face including a groove is formed in each resin member, and in which a contact face is formed on one of the resin members;
sandwiching the shielded wire and the sheathed wire between the pair of resin members such that the grooves face with each other while accommodating the sheathed wire therein;
providing an ultrasonic horn having a contact face;
contacting the contact face of the ultrasonic horn with the contact face of the resin member; and
applying ultrasonic vibration to thermally fuse and integrate the bonding faces of the resin members with each other, while thermally fusing a part of the second insulating sheath and a part of the third insulating sheath so that the conductive cover member and the second conductive core wire are electrically connected,
wherein at least one of the contact face of the ultrasonic horn and the contact face of the resin member is formed with a recessed portion.
Preferably, the recessed portion is situated at a position opposing to a position at which the conductive cover member and the second conductive core wire are electrically connected.
Preferably, at least one protrusion is formed on at least one of the bonding faces. The ultrasonic vibration is applied such that ultrasonic waves are concentrated to the protrusions to thermally fuse at least the protrusion while integrating the bonding faces of the resin members with each other
Here, it is preferable that the protrusion includes a pair of protrusions formed at both sides of at least one of the groove so as to extend therealong.
Here, it is preferable that the protrusion includes two pairs of protrusions formed at both sides of the grooves so as to be abutted on each other in the sandwiching step.
Preferably, the second conductive core wire is a plated wire having a melting temperature which is lower than a temperature of an internal heat generated by the ultrasonic vibration.